PP Fiber Research Articles

Influence of Processing Temperature on Microcellular Injection‐Moulded Wood–Polypropylene Composites

AbstractSummary: Microcellular wood fibre reinforced polymer materials are significant because of their possibility to reduce the density of automotive components through microcellular structure, process and product part advantages, and as a new development with bio‐fibre strengthened plastics. Soft wood fibre reinforced PP composites in box part and panel shape were prepared by an injection moulding process. Polymeric microspheres as a chemical foaming agent (endothermic) were used to produce the microcellular composites. The influence of injection moulding processing temperature on the microcellular structure and properties (tensile and flexural properties, notched charpy impact strength) was investigated by varying the temperature over the 150–170 °C, 160–180 °C and 170–190 °C. A comparative study of cell morphology, weight reduction and mechanical properties was conducted between box part and panel. Microcell morphology, cell size, shape and distribution were investigated using scanning electron micrographs. The results indicated that the lower processing temperature should be below the range of 170–190 °C and processing temperature at 160–180 °C, where the composites showed finer cellular structure compared to other processing temperatures. The mechanical properties did not differ with the variation of processing temperature regardless of composite types (box part or panel). Cellular structure changes in the box part were found considering near or far from injecting point.Microcellular injection‐moulded box part (geometry: 150 × 100 × 70 mm3 in size) of soft wood fibre–PP composites.magnified imageMicrocellular injection‐moulded box part (geometry: 150 × 100 × 70 mm3 in size) of soft wood fibre–PP composites.

Strength of Unidirectional Short Fiber Structures as a Function of Fiber Length

The strength of super-oriented polymer fibers or unidirectional short fiber composites strongly depends on the length of the molecule chains or the reinforcing fibers, respectively. A simple statistical model is developed based on the theory of fiber flows and the strength of the structure and its dependence on fiber length are determined in case of fibers broken or damaged owing to parting rigidly from the environment simultaneously. Later, two new special and modified versions of the so-called ES-bundle and one of the idealized statistical fiber-bundle-cells developed earlier, are introduced and applied to model the breaking process of the fibrous structure at different damage modes and its dependence on the fiber length is analyzed. In case of constant fiber length, a simple analytical relationship between the mean tensile strength and the fiber length is obtained which is valid for all the cases discussed. On the basis of the results, formulas are developed to estimate the strength of short fiber composites as a function of fiber length and fiber content, as well as to model the effect of the reduction in the fiber adhesion in case of a very small matrix content. The practical applicability of the results is demonstrated by identifying the relationship between tensile strength and molecule mass of PP fibers.

Development and characterization of self‐reinforced poly(propylene) composites: carded mat reinforcement

AbstractSelf‐reinforced poly(propylene) (PP) composites were produced by film‐stacking using carded mats of α‐isotactic PP fibers and films of β‐isotactic PP. Composite sheets were produced at various consolidation temperatures (T = 150–170°C) and constant holding time (t = 2 min). In a test series the holding time was varied (t = 2–20 min) by keeping the consolidation temperature constant. The consolidation degree of the sheets was studied on polished sections by light microscopy and quantified by density and peel test results. Specimens cut of the sheets were subjected to in‐plane static tensile and out‐of‐plane dynamic impact (instrumented falling weight impact, IFWI) tests. It was established that the best indicators for the consolidation degree are the density, tensile strength and specific perforation impact energy and between them linear correlations exists. Increasing the density of the composites resulted in increased tensile strength (due to lower void content and better fiber/matrix adhesion) and reduced perforation impact energy (due to hindered delamination between the constituent layers). Copyright © 2006 John Wiley & Sons, Ltd.

Production and use of polypropylene fibres and yarn

World production of PP fibres in 2004 was approximately 6.3 million tons, including 2.1 million tons of film fibres. The total consumption of PP fibres, including spunbond/meltblown, on the European continent increased by 2.5% in 2004, reaching 2.4 million tons. In the near future, expansion of use of PP fibres for production of nonwovens is projected. The world market capacity will increase by 2008 to 3.55 million tons, including up to 1.0 million tons in North American countries. A wide assortment of PP products in the form of films, ribbons, fibrillized materials, staple fibre, complex yarns, spunbond, meltblown, etc., for manufacturing bags, soft containers, agrotextiles, packaging, cables, carpets, hygienic and medical goods, etc., has been developed.

Crystal morphology and tensile properties of LLDPE containing PP fibers as obtained via dynamic packing injection molding

The fibrillated linear low-density polyethylene (LLDPE)/isotactic polypropylene (iPP) fiber blends were subjected to dynamic packing injection molding (DPIM), in which the prolonged shear was exerted on the melt during solidification stage. Transcrystallization of LLDPE on PP fibers, with stacked lamellae parallel to each other and aligned approximately perpendicular to the long axial of the fibers, has been achieved for the first time in DPIM due to the prolonged shear. PP fibers were found to align parallel to the flow direction along thickness up to the oriented zone of sample prepared by DPIM. The presence of oriented PP fibers enhanced the orientation of LLDPE that developed row-nucleated type morphology. The molding temperatures were changed between 160 °C and 200 °C to investigate the effect of molding temperature on the crystalline microstructure of the blends. As increasing the molding temperature from 160 °C to 200 °C, the partial melting of PP fiber was changed to complete melting, resulting in a dramatic change of the crystal morphology and the mechanical properties as well.

Micro-Raman study of the fatigue and fracture behaviour of single PA66 fibres: Comparison with single PET and PP fibres

The micro/nano-structural evolution before and after tensile loading, fatigue and ultimately, failure has been studied by Raman microspectroscopy for PA66, PP, PBO and PET single fibres and precursors, using two probes: low wavenumber collective modes at <150 cm −1 as representative of the crystalline and amorphous chains and stretching and bending modes, as representative of the C–C bond local behaviour. Wavenumber and bandwidth distributions across fibre/precursors diameters reveal different types of skin/core heterogeneity. The in situ analysis at different strain levels shows that amorphous chains in the fibre accommodate the stress differently. Slight tensile straining is observed for crystalline PA 66 chains, and compression for PP and PET chains indicating different local chain architectures. The post mortem analysis of a series of fibres failed in fatigue tests shows that amorphous domains are highly stressed during the failure and a remnant stress can be measured.

Morphology and Structure of Constituent Fibres in Thermally Bonded Nonwovens

A new process has been developed to produce three-dimensional nonwovens directly from staple fibres. In order to establish suitable windows of the process parameters to achieve high-quality nonwoven products, the effects of thermal bonding temperature, dwell time and mould material on the morphology and structure of the fibre have been investigated using PP/PET bi-component fibres. It was evident from both scanning electron microscope images and Raman spectra that thermal-induced shrinkage of the PP sheath fibre occurred in the thermal bonding process, leading to deformation and cracking of the PP sheath and exposure of the PET core. X-ray diffraction results revealed crystal imperfection and/or less ordered polymer chains, more γ-form and thermal contraction of the crystal lattice for the PP sheath fibre, while birefringence measurements indicated that both the birefringence and the orientation factor for the PP fibre decreased after the thermal bonding process. The degrees of the thermal-induced shrinkage increased, and the crystallinity, birefringence and orientation factor of the PP sheath fibre decreased with increasing thermal bonding temperature, dwell time and thermal conductivity of the mould material. All these can be attributed to the different levels of modification of chemical composition caused by thermal oxidative degradation and thermal-induced relaxation of the orientation during the thermal bonding process.

Effect of coupling agent on abrasive wear behaviour of chopped jute fibre-reinforced polypropylene composites

In this paper, studies have been conducted to investigate the abrasive wear behaviour of jute fibre-reinforced polypropylene composites. Effect of addition of maleic anhydride-grafted polypropylene (MA-g-PP)-coupling agent by two different approach, sliding distance and load on abrasive wear performance of jute fibre–PP composites has been determined by using a SUGA abrasion tester. Use of coupling agent gives better wear resistance as compared to without the use of coupling agent. It has also been found that addition of MA-g-PP coupling agent during melt mixing gives better wear resistance as compared to the jute PP composites having MA-g-PP solution-treated jute fibres, which has been explained on the basis of highest thermal stability of jute–PP Composite having melt-mixed MA-g-PP. Abrasive wear performance of the composites has been explained with the help of surface microstructures of worn surfaces.

중심 축하중을 받는 고강도 RC기둥의 섬유 혼입량에 따른 폭열 및 내화 성상

This paper investigates experimentally the fire resistance performance and spatting resistance of high performance reinforced concrete column member subjected to fire containing polypropylene fiber(PP fiber) and cellulose fiber(CL fiber). An increase in PP fiber and CL fiber contents, respectively resulted in a reduction of fluidity due to fiber ball effect. Air content is constant with m increase in fiber content. Compressive strength reached beyond 50 MPa. Based on fire resistance test, severe failure occurred with control concrete specimen, which caused exposure of reinforcing bar. No spall occurred with specimen containing PP fiber. This is due to the discharge of internal vapour pressure. Use of CL fiber superior to control concrete in the side of spatting resistance, localized failure at comer of specimen was observed. Corner of specimen had deeper neutralization than surface of specimen. Specimen containing PP fiber had the least damaged area due to spatting. Neutralization depth ranged between 6 and 8 mm Residual compressive strength of specimen containing PP fiber maintained 40%, which is larger than control concrete with 20% of residual strength. Specimen containing CL fiber had 25% or residual strength.

The influence of fibre length and concentration on the properties of glass fibre reinforced polypropylene: 7. Interface strength and fibre strain in injection moulded long fibre PP at high fibre content

The mechanical performance of injection moulded long glass fibre reinforced polypropylene with a glass fibre content in the range 0-73% by weight has been investigated. The composite modulus exhibited a linear dependence on fibre content over the full range of the study. Composite strength and impact resistance exhibited a maximum in performance in the 40-50% by weight reinforcement content range. The residual fibre length, average fibre orientation, interfacial shear strength, and fibre strain at composite failure in the samples have been characterised. These parameters were also found to be fibre concentration dependent. The interfacial shear strength was found to be influenced by both physical and chemical contributions. Theoretical calculations of the composite strength using the measured micromechanical parameters enabled the observed maximum in tensile strength to be well modelled.

Polypropylene Fibers Modified by Plasma Treatment for Preparation of Ag Nanoparticles

A novel method for preparing poly(propylene-graft-2-methacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester)-silver fibers (PPG-IAg fibers) by plasma-induced grafting polymerization is presented in this study. The chelating groups, -N(CH2COO-)2 (GMA-IDA), on the surface of the PPG-I fibers are the coordination sites for chelating silver ions. At these sites, Ag nanoparticles were grown first by reduction with UV light with a wavelength of 366 nm, and second, through immersion in a 24% formaldehyde solution with pH values set variously at 2, 5, 8, and 11. The characteristics of the PPG-I fibers with differing durations of plasma treatment were monitored by using a Fourier transform infrared (FT-IR) spectroscope. Scanning electronic microscopy (SEM) and elemental analysis show that the percentage of GMA-IDA grafted onto PP fiber reaches a maximum when the plasma treatment time is 3 min. Plasma treatment time beyond a certain length of time results in an abundance of free radicals and causes considerable cross-linking on the fiber surface which thus decreases the extent of grafting. Moreover, the crystalline phase of Ag nanoparticles is identified by using X-ray diffraction (XRD). When the PPG-I fibers are reduced by the UV light method, SEM and TEM microscopes reveal that the size of the Ag nanoparticles on the fiber surface decreases significantly with the increase of pH values in aqueous solutions. Notably, in the reduction of formaldehyde solution, the particle size of Ag nanoparticles reaches a minimum at the lowest pH value. The TEM observations show that Ag nanoparticles are distributed both in the exterior and interior of the grafting layer. In addition, under high pH values the distribution of the Ag nanoparticles permeate more deeply in the GMA-IDA grafting layer due to the swelling effect of the GMA-IDA polymer.

Finite element analysis of various methods for protection of concrete structures against spalling during fire

A mathematical model of hygro-thermo-mechanical phenomena in heated concrete, treated as multiphase porous material is briefly presented. Some modifications necessary to analyse high–temperature performance of a concrete containing the PP-fibres have been introduced, experimentally validated and applied for analysis of performance of a concrete tunnel lining during a 10-MW fire and the ISO standard fire. Three methods for protecting concrete structures against excessive degradation in fire conditions have been numerically analysed by means of the computer model. The analysed protection methods are based either upon application on a structure surface of a reflective layer, or covering it with a protective layer made of a very porous concrete or an addition of the PP fibres to the concrete mix. Efficiency of these methods has been numerically analysed in thermal conditions corresponding to the ISO-834 standard fire. The results obtained show that even relatively simple methods, like application a protective layer or increasing the surface reflectance, can retard to some extent concrete degradation during a fire.

Structural dependence of the deformation characteristics of polypropylene film fibre in stress relaxation

The deformational rigidity increases due to relaxation of stresses in oriented PP fibres. Elongation of PP fibres is accompanied by mechanical failure in all stages, which is a distinctive feature of deformation processes in these materials. Ordering of the structure of amorphous regions, manifested by an increase in the deformational rigidity of these fibres, is the result of stress relaxation in oriented PP fibres.

Abrasion Properties of Polypropylene/Polyamide 6 Blend Fiber

In industrial materials, tribological properties of fibers are one of very important practical properties. To make high abrasion resistance fibers, Polypropylene/Polyamide 6 (hereafter “PP/PA6”) blend fibers of different blend ratios and viscosity ratios were prepared. The relationship between abrasion property and blend ratio of the blend fibers showed that the abrasion resistance increased by blending PA6 by about 20% compared with pure PP fiber, and that the abrasion resistance decreased as more PA6 was blended. Pure PA6 fiber (PA6 content=100%), however, showed a high abrasion resistance. Namely, the relationship between abrasion resistance and blend ratio of the blend fibers was shown in a reverse-S-shaped curve.Then, abrasion property was studied for blend fibers of different viscosity ratios (ηPP/ηPA6). The results showed that the blend fiber of a viscosity ratio value smaller than 1 had relatively low abrasion resistance even for equivalent PA6 content, and that abrasion resistance increased as viscosity ratio increased. Investigation of the composition of the fiber surface by FTIR-ATR proved that as the abrasion resistance of the blend fiber increased, the content of the PA6 component on the surface increased. Blend fibers of viscosity ratio value more than 1 had considerable abraded powder on the fiber surface after abrasion, indicating further improvement of abrasion resistance. These results indicate that a blend fiber of a large viscosity ratio has a higher abrasion resistance than pure PA6 fiber and PP fiber.

Intentional regulation of the structure and properties of cation-exchange fibre composites based on polypropylene fibres

An analysis of the structural features and properties of the developed cation-exchange fibre composites showed that shaped PP fibres, which are chemically inert compounds, actively participate in crosslinking processes in cation-exchange fibre materials (CEFMM) as a result of additional surface modification. Additional cryo treatment of shaped PP fibres improves their transport and sorption properties and increases the proportion of synthesized cation-exchange matrix, which is also responsible for elevated performance properties.

Injection moulded microcellular wood fibre–polypropylene composites

Abstract The polymer–wood fibre composites utilize wood fibres as a reinforcing filler in the polymer matrix and are known to be advantageous over the neat polymers in terms of the materials cost and some mechanical properties such as stiffness and strength. These wood fibre composites are microcellular processed to create a new class of materials with unique properties. Recent studies have demonstrated the feasibility of developing microcellular structures in polymer–wood fibre composites. An experimental investigation was conducted to research the microcellular behaviour in the injection moulding foam processing of polypropylene–wood fibre composites using chemical foaming agents. The effects of fibre type (hard and soft wood fibre) and different chemical foaming agents (endothermic, exothermic and endo/exothermic) on the density, physico-mechanical properties, surface roughness and cell morphology of foamed PP–wood fibre composites are studied. A compatibiliser maleic anhydride polypropylene copolymer (MAH-PP) was used with the intension of improving the mechanical properties of foamed composites. The structures of the foamed composites were examined using scanning electron microscopy and optical microscopy to determine the cell size, shape and distribution of cells to account for this behaviour. The density of microfoamed hard wood fibre–PP composites reduced around 30% and decreased up to 0.741 g/cm3 with the using of exothermic chemical foaming agent. Optical microscopy showed that the cells are round and cell sizes are affected by chemical foaming agents. Tensile and flexural tests are performed on the foamed composites to investigate the dependence of these properties on the density (specific properties) of foamed specimens and compared with non-foamed composites and MAH-PP has improved the physico-mechanical properties up to 80%. Chemical foaming agents have also an effect on surface roughness of the composites which decreased surface roughness of the foamed composites compared to the non-foamed composites. Water absorption and thickness swelling of the composites investigated also.

Improving Wood/Polypropylene fiberboards properties with an original MAPP coating process

In this work, which is part of a project about WPC fibreboard (Wood Polymer Composites) with post mouldable ability, we focused on the role of interface modification in improving physical and mechanical properties. To reach these goals, an original coating process was developed. Rather than randomly disperse a coupling agent powder in the mat, the coupling agent was aimed at the interface by coating MAPP onto PP fibre, which is less important in quantity than natural fibre in our WPC. In that way the bonding improvement was concentrated at the interface where the stress transfer occurs. Results of internal bond, flexion and tensile testing showed improvements of WPC fibreboards mechanical characteristic. SEM corroborated the presence of MAPP coating and validated experimental process.

The impermeability mechanism of self-compacting water proof concrete

The impermeability mechanism of water-proof self-compacting concrete (WPSCC) was studied. The mechanism and influential factors, such as water-cement ratio (w/c), dosage of powder, superplasticizer, sand content, aggregate content, fly ash, UEA, PP fiber, on compactibility and crack resistance of WPSCC were analyzed. A type of WPSCC successfully applied in tunnel liner with its validities, conveniences and economies by mockup test was developed and optimized. Experimental results show that the WPSCC has good workability, mechanical properties and impermeability when reasonable requirements are fulfilled.

Mass transfer analysis on air stripping of VOCs from water in microporous hollow fibers

The air stripping removal of VOCs such as toluene and phenol from water in microporous PP hollow fibers was studied. The VOC stream passed through the lumen side of the module, while air (stripping gas) flowed across the shell side. Experiments were performed at different liquid flow rates (8–16 cm 3/min), gas flow rates (60–180 cm 3/min), feed VOC levels (100–1000 ppm), and temperatures (24–35 °C). It was shown that the removal was more effective when feed VOC level, liquid or gas flow rate increased. The applicability of a mass transfer model that considers diffusion in the liquid layer, membrane, and gas layer under steady state was checked. Unlike phenol with a very small dimensionless Henry's law constant (equilibrium gas concentration divided by liquid concentration) and a relatively low amount of sorption on PP fibers, the measured overall mass transfer coefficients for toluene reasonably agreed with those predicted from the model. The large deviation observed for phenol indicated unsteady state nature, likely due to its small concentration difference between air and liquid phase/fiber matrix. The air stripping removal and separation of binary VOCs including o-xylene and chloroform from water was finally examined.

The influence of fibre length and concentration on the properties of glass fibre reinforced polypropylene. 6. The properties of injection moulded long fibre PP at high fibre content

The results of an investigation of the mechanical performance of injection moulded long glass fibre reinforced polypropylene with a glass fibre content in the range 0–73 wt% are presented. The composite modulus exhibited a linear dependence on fibre content over the full range of the study. Composite strength and impact resistance exhibited a maximum in performance in the 40–50 wt% reinforcement content range. The residual fibre length and fibre orientation in the samples has also been characterised. These parameters were also found to be fibre concentration dependent. Modelling of the composite strength using the measured fibre length and orientation data did enable a maximum in strength to be predicted. However, the position and absolute level of the predicted maximum did not correlate well with the experimental data. Further analysis indicated that deeper investigation of the dependence of the interfacial shear strength and fibre stress at composite failure on the fibre content are required to fully elucidate these results.